> Hello fine folks of the Neonixie community, I'll lay out the scenario here my > troubles are at the bottom. I am working on an interesting computer case > project in which i would like to use 2 IN-13's or IN-9's (I have some of > both) to drive some meters for my computer (CPU usage, Temperature, VU, ect.). > > Components I am using, Or at least intend to use include > > PSU - > http://www.ebay.com/itm/High-Voltage-Power-Supply-Kit-45V-to-190V-Out-for-Nixie-Old-Radio-Kit-/251228875692?pt=LH_DefaultDomain_0&hash=item3a7e686bac > > Vishay H11D3-X007 Optocouplers > http://pdf1.alldatasheet.com/datasheet-pdf/view/230514/VISHAY/H11D3-X007.html
Note that this link won't work, as the alldatasheet people don't accept foreign links directly to their data pages. It's probably easier just to link to the manufacturer's data sheet: http://www.vishay.com/docs/83611/83611.pdf > Arduino to communicate with the computer and output PWM Okay, you're trying to solve two problems here. One is that you're using PWM as an analog output. It isn't really analog, it's a pulse with a varying duty cycle. You need to filter it to get an analog signal. While you can modulate the (apparent) brightness of an LED just fine with a PWM signal, it won't work with these displays, it will just turn them on and off rapidly, changing the brightness but not the lit length. The second problem is the optocoupler. I'm not sure why you're using one in the first place - normally when driving these displays, they're current modulated by a high voltage transistor at the ground end. Optocouplers aren't very linear either, which makes things harder, unless you're coupling the PWM through the optocoupler and filtering it to an analog signal on the other side. You'll also need a current limiting resistor between your Arduino I/O pin and the optocoupler - without it, the LED will try to draw too much current from the Arduino, and things won't work right. I like the project, and we're willing to help you, but let's start with a few questions. Are you converting your PWM signal to analog with a filter? The filter is very simple, just a resistor and a capacitor. Where are you doing your PWM to analog conversion, before or after the optocoupler? Why are you using an optocoupler in the first place? > I have experimented with several different configurations, done all of the > calculations i am smart enough to achieve (Not very many of them unfotunately) We're happy to walk you through the calculations, but first we need to know what configurations you've tried, and what your current one is. > Please Please Please, Can someone help me to figure out the proper resistance > vals between the Arduino and my optocoupler and between the cathode and > ground. Between the Arduino and the optocoupler, there are two choices, you can run from the I/O pin to +5V or from the I/O pin to ground. Either can work, and happily the resistor is the same either way. I'm going to assume you're running your optocoupler in digital mode, and converting your PWM to analog on the other side. To get a decent current flow through the output transistor, you'll need to push 10mA or so through the LED. From the data sheet, the LED will have a voltage drop of 1.1V at this current. Armed with that, you can use Ohm's law to figure the resistance. The voltage across the resistor will be 5 volts (your Arduino supply voltage*) minus the LED voltage of 1.1V, which works out to 3.9V. You want 10mA through this resistor to drop those 3.9V. 10mA is 0.01A, and it's generally worthwhile to work Ohm's law directly using amps, volts, and ohms. Ohm's law says E=IR, or voltage equals current times resistance. For this problem, you get 3.9V = 0.01A * R. Multiply both sides by 100, and you get 390Ω. Happily, that's a common value, but 330Ω is close enough. You can figure the current for that too, again using Ohm's law: 3.9 = 330I, which works out to 11.8mA, which is just fine. Note that I'm assuming here that the LED voltage won't change too much with the current - it's actually a workable assumption here, but I thought I'd make it clear that I'm making it. * unless you're using a 3.3V Arduino As for cathode and ground, I'm not quite sure what your lashup looks like. It sounds like you're trying to use the optocoupler as a high-side switch, and putting the current limiting resistor on the low side. That's a valid approach, but a little peculiar. > Thank you all for your patience with this newbie Hey, we were all newbies once! And I remember being thrilled to get help, so I'm happy to help others. > P.S. I am willing to learn or do research on my own if you can even point me > in the right direction. Sounds like you've done some solid thinking so far, but like I said, you're trying to do a complicated thing, so there will be some unknowns. Once we know more about how you're trying to get this to work, we can hopefully be more help. Cheers, John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
